package n71_享元模式;

import lombok.extern.slf4j.Slf4j;

import java.sql.*;
import java.util.Map;
import java.util.Properties;
import java.util.Random;
import java.util.concurrent.Executor;
import java.util.concurrent.atomic.AtomicIntegerArray;

import static utils.Sleeper.sleep;

/**
 * @author fu
 * @date 2022-02-20 18:40
 * 概要：
 * ---------------------------------------------------------------
 * |                                                              |
 * |                  |
 * |                                                             |
 * |=============================================================
 */
@Slf4j(topic = "c.T1")
public class T1_diy_数据库连接池 {

    public static void main(String[] args) {

        // 连接池  ； 创建 两个连接
        final Pool pool = new Pool(2);

        for (int i = 0; i < 5; i++) {

            new Thread(()->{

                // 借连接
                Connection borrow = pool.borrow();
                sleep(new Random().nextInt(10));

                // 还连接
                pool.free(borrow);

            }).start();
        }

    }

}
// 自定义数据库连接池类
@Slf4j(topic = "c.Pool")
class Pool {
    // 1. 连接池大小
    private final int poolSize;

    // 2. 连接对象 数组
    private Connection[] connections;

    // 3. 连接状态 数组 0空闲 1繁忙
    private AtomicIntegerArray states;

    // 4. 构造方法
    public Pool(int poolSize) {
        this.poolSize = poolSize;
        this.connections = new Connection[poolSize];
        this.states = new AtomicIntegerArray(poolSize);

        // 初始化连接池 连接对象
        for (int i = 0; i < poolSize; i++) {
            this.connections[i] = new MockConnection("连接池"+i);
        }
    }

    // 5. 借连接 【所有线程 可访问，有竞争】
    public Connection borrow(){
        while (true){
            // 遍历状态数组 ；检查空闲的 & 改为繁忙
            for (int i = 0; i < poolSize; i++) {
                if (states.get(i) == 0){
                    //  注意： 不能states.set(i,0);   会有线程安全问题
                    if (states.compareAndSet(i, 0, 1)) {
                        log.debug("borrow - {}", connections[i]);
                        return connections[i];
                    }
                }
            }
            // 如果 没有 空闲连接 ==>>> 当前线程进入等待 【不去空转，不占用CPU资源】
            synchronized (this){
                try {
                    log.debug("wait...");
                    this.wait();
                } catch (InterruptedException e) {
                    e.printStackTrace();
                }
            }
        }
    }

    // 6. 归还连接  对于当前方法【所有线程 可访问，有竞争】
    public void free(Connection conn){

        // 对于 for循环内 【当前 连接池的所有者 ，无竞争】
        for (int i = 0; i < poolSize; i++) {
            if (connections[i].equals(conn)) {
                states.set(i, 0);
                synchronized (this){
                    log.debug("free ------ {}", conn);
                    this.notifyAll();
                }

                break;
            }
        }
    }
}

// 虚假数据库连接
class MockConnection implements Connection{

    private String name;

    public MockConnection(String name){
        this.name = name;
    }

    @Override
    public String toString() {
        return "MockConnection{" +
                "name='" + name + '\'' +
                '}';
    }

    @Override
    public Statement createStatement() throws SQLException {
        return null;
    }

    @Override
    public PreparedStatement prepareStatement(String sql) throws SQLException {
        return null;
    }

    @Override
    public CallableStatement prepareCall(String sql) throws SQLException {
        return null;
    }

    @Override
    public String nativeSQL(String sql) throws SQLException {
        return null;
    }

    @Override
    public void setAutoCommit(boolean autoCommit) throws SQLException {

    }

    @Override
    public boolean getAutoCommit() throws SQLException {
        return false;
    }

    @Override
    public void commit() throws SQLException {

    }

    @Override
    public void rollback() throws SQLException {

    }

    @Override
    public void close() throws SQLException {

    }

    @Override
    public boolean isClosed() throws SQLException {
        return false;
    }

    @Override
    public DatabaseMetaData getMetaData() throws SQLException {
        return null;
    }

    @Override
    public void setReadOnly(boolean readOnly) throws SQLException {

    }

    @Override
    public boolean isReadOnly() throws SQLException {
        return false;
    }

    @Override
    public void setCatalog(String catalog) throws SQLException {

    }

    @Override
    public String getCatalog() throws SQLException {
        return null;
    }

    @Override
    public void setTransactionIsolation(int level) throws SQLException {

    }

    @Override
    public int getTransactionIsolation() throws SQLException {
        return 0;
    }

    @Override
    public SQLWarning getWarnings() throws SQLException {
        return null;
    }

    @Override
    public void clearWarnings() throws SQLException {

    }

    @Override
    public Statement createStatement(int resultSetType, int resultSetConcurrency) throws SQLException {
        return null;
    }

    @Override
    public PreparedStatement prepareStatement(String sql, int resultSetType, int resultSetConcurrency) throws SQLException {
        return null;
    }

    @Override
    public CallableStatement prepareCall(String sql, int resultSetType, int resultSetConcurrency) throws SQLException {
        return null;
    }

    @Override
    public Map<String, Class<?>> getTypeMap() throws SQLException {
        return null;
    }

    @Override
    public void setTypeMap(Map<String, Class<?>> map) throws SQLException {

    }

    @Override
    public void setHoldability(int holdability) throws SQLException {

    }

    @Override
    public int getHoldability() throws SQLException {
        return 0;
    }

    @Override
    public Savepoint setSavepoint() throws SQLException {
        return null;
    }

    @Override
    public Savepoint setSavepoint(String name) throws SQLException {
        return null;
    }

    @Override
    public void rollback(Savepoint savepoint) throws SQLException {

    }

    @Override
    public void releaseSavepoint(Savepoint savepoint) throws SQLException {

    }

    @Override
    public Statement createStatement(int resultSetType, int resultSetConcurrency, int resultSetHoldability) throws SQLException {
        return null;
    }

    @Override
    public PreparedStatement prepareStatement(String sql, int resultSetType, int resultSetConcurrency, int resultSetHoldability) throws SQLException {
        return null;
    }

    @Override
    public CallableStatement prepareCall(String sql, int resultSetType, int resultSetConcurrency, int resultSetHoldability) throws SQLException {
        return null;
    }

    @Override
    public PreparedStatement prepareStatement(String sql, int autoGeneratedKeys) throws SQLException {
        return null;
    }

    @Override
    public PreparedStatement prepareStatement(String sql, int[] columnIndexes) throws SQLException {
        return null;
    }

    @Override
    public PreparedStatement prepareStatement(String sql, String[] columnNames) throws SQLException {
        return null;
    }

    @Override
    public Clob createClob() throws SQLException {
        return null;
    }

    @Override
    public Blob createBlob() throws SQLException {
        return null;
    }

    @Override
    public NClob createNClob() throws SQLException {
        return null;
    }

    @Override
    public SQLXML createSQLXML() throws SQLException {
        return null;
    }

    @Override
    public boolean isValid(int timeout) throws SQLException {
        return false;
    }

    @Override
    public void setClientInfo(String name, String value) throws SQLClientInfoException {

    }

    @Override
    public void setClientInfo(Properties properties) throws SQLClientInfoException {

    }

    @Override
    public String getClientInfo(String name) throws SQLException {
        return null;
    }

    @Override
    public Properties getClientInfo() throws SQLException {
        return null;
    }

    @Override
    public Array createArrayOf(String typeName, Object[] elements) throws SQLException {
        return null;
    }

    @Override
    public Struct createStruct(String typeName, Object[] attributes) throws SQLException {
        return null;
    }

    @Override
    public void setSchema(String schema) throws SQLException {

    }

    @Override
    public String getSchema() throws SQLException {
        return null;
    }

    @Override
    public void abort(Executor executor) throws SQLException {

    }

    @Override
    public void setNetworkTimeout(Executor executor, int milliseconds) throws SQLException {

    }

    @Override
    public int getNetworkTimeout() throws SQLException {
        return 0;
    }

    @Override
    public <T> T unwrap(Class<T> iface) throws SQLException {
        return null;
    }

    @Override
    public boolean isWrapperFor(Class<?> iface) throws SQLException {
        return false;
    }
}